syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5784/2:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=81637, q=23 ncpus=2)
task:syz-executor    state:R  running task     stack:20528 pid:5784  ppid:5781   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7009
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:seqcount_lockdep_reader_access+0x17e/0x1c0 include/linux/seqlock.h:105
Code: ff 4d 85 ed 75 16 e8 b1 57 8b ff eb 15 e8 aa 57 8b ff e8 c5 95 74 08 4d 85 ed 74 ea e8 9b 57 8b ff fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 27 00 00 00 00 66 43 c7 44 27 09 00 00 43 c6 44 27 0b 00
RSP: 0018:ffffc900045e7880 EFLAGS: 00000293
RAX: ffffffff81fa37f5 RBX: 0000000000000000 RCX: ffff88802ac21e00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900045e7928 R08: ffffffff90da853f R09: 1ffffffff21b50a7
R10: dffffc0000000000 R11: fffffbfff21b50a8 R12: dffffc0000000000
R13: 0000000000000200 R14: ffffffff81fa171f R15: 1ffff920008bcf10
 read_seqbegin include/linux/seqlock.h:893 [inline]
 read_seqbegin_or_lock include/linux/seqlock.h:1187 [inline]
 prepend_path+0x29f/0x960 fs/d_path.c:171
 d_absolute_path+0xa2/0x140 fs/d_path.c:234
 tomoyo_get_absolute_path security/tomoyo/realpath.c:101 [inline]
 tomoyo_realpath_from_path+0x2d9/0x5d0 security/tomoyo/realpath.c:271
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x20f/0x4b0 security/tomoyo/file.c:822
 tomoyo_path_unlink+0xa3/0xe0 security/tomoyo/tomoyo.c:161
 security_path_unlink+0xdc/0x130 security/security.c:1767
 do_unlinkat+0x2a2/0x570 fs/namei.c:4396
 __do_sys_unlink fs/namei.c:4447 [inline]
 __se_sys_unlink fs/namei.c:4445 [inline]
 __x64_sys_unlink+0x49/0x50 fs/namei.c:4445
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f258098ec77
RSP: 002b:00007ffc17c5fdd8 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f258098ec77
RDX: 00007ffc17c5fe00 RSI: 00007ffc17c5fe90 RDI: 00007ffc17c5fe90
RBP: 00007ffc17c5fe90 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000206 R12: 00007ffc17c60f20
R13: 00007f2580a11d7d R14: 00000000000d5670 R15: 00007ffc17c60f60
 </TASK>
rcu: rcu_preempt kthread starved for 10335 jiffies! g81637 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:26888 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:148
Code: cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d c3 64 39 00 f3 0f 1e fa fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc 66 0f 1f 00 55 41 57 41 56
RSP: 0018:ffffc90000187de0 EFLAGS: 000002c2
RAX: 7700bc457d3e9e00 RBX: ffffffff816187ab RCX: 7700bc457d3e9e00
RDX: 0000000000000001 RSI: ffffffff8aaabce0 RDI: ffffffff8afc6b00
RBP: ffffc90000187f20 R08: ffff8880b8f36b2b R09: 1ffff110171e6d65
R10: dffffc0000000000 R11: ffffed10171e6d66 R12: ffffffff8e4a8d68
R13: 0000000000000001 R14: 0000000000000001 R15: 1ffff1100364e780
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2e915ff8 CR3: 000000007847b000 CR4: 00000000003526e0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:753
 default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
 cpuidle_idle_call kernel/sched/idle.c:170 [inline]
 do_idle+0x1eb/0x510 kernel/sched/idle.c:282
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:380
 start_secondary+0xee/0xf0 arch/x86/kernel/smpboot.c:323
 secondary_startup_64_no_verify+0x179/0x17b
 </TASK>